1. Field of the Invention
The invention relates to a pairing device between decoders divided into one master decoder and slave decoders as well as a process enabling this pairing. The invention also relates to a satellite reception system including this device.
Multimedia service operators distribute their services according to several transmission networks. Among these networks, the satellite, cable and digital terrestrial distribution networks can be cited. These different distribution networks have in common the specific feature of bringing data flows to a device, entry point of the network, in the home. The services are then distributed in the home to different areas where the subscriber wants to be able to receive them. The reception itself is carried out by means of device called a digital decoder whose function is to check the access rights of the subscriber to the services and to decode those services for which the subscriber has rights.
In his home, the subscriber often has several receivers capable of displaying the services distributed. The problem then arises of enabling the subscriber to decode the services to which he has subscribed, in several areas of the home. The distribution of the decoded service downstream from the decoder, called master decoder, is one solution. If you want to allow each point of visualisation of the service in the home to display any service independently from the services displayed on the other points of visualisation, several decoders must be used in the home, that is one decoder per point of visualisation, each decoder being able to decode any of the services independently from the services decoded by the other decoders in the home. To achieve this, it is thus possible to use several decoders, called slaves, in the home.
The pairing between a master decoder and several slave decoders requires a pairing accessory circuit 3 situated in the reception system comprising an antenna 1, a receiver block called an LNB (Low Noise Block) 2 and connected to the decoders, as shown in FIG. 1. It sets up a communication link between the different master 5 and slave 6, 7, 8 decoders.
2. Description of the Prior Art
Such a circuit is known in the prior art. The patent FR 0213460 describes this circuit shown in FIG. 2. This coupling circuit 100 comprises two inputs/outputs of signals I/O3 and I/O4 designed to be connected to the decoders 5, 6. It also comprises at least two inputs/outputs I/O1 and I/O2 designed to be connected respectively to the LNB block 2 associated with the antenna 1. A band-pass filter 150 links the first inputs/outputs of signals I/O3 and I/O4 between each other, enabling a connection limited to a communication band frequency to be realised, for the dialogue between the different master 5 and slave 6 decoders. The inputs/outputs I/O1 and I/O2 are connected respectively to the inputs/outputs of the signals I/O3 and I/O4 by means of band rejector filters 101 and 102 that reject the frequency band corresponding to the communication channel used by the decoders.
Such a coupling device can be extended to N inputs/outputs. Each addition of a pair of inputs/outputs adds a band-pass filter 150 and a band rejector filter 103, as shown by the dotted lines.
The UHF-VHF signals received by antennas 1 then sent to the circuit on inputs I/O1, I/O2 are then sent to the decoders connected to the inputs/outputs I/O3, I/O4.
The decoders connected to the inputs/outputs I/O3, I/O4, are controlled by exchanging data on the communication channel between the master decoder connected to one of the outputs and the slave decoders connected to the other outputs. The signals sent by this master decoder to organise the control of the other decoders called slaves are signals in a frequency band not disturbing the reception.
However, such a control of the slaves has many disadvantages, particularly when the number of slave decoders is large. Indeed, all the slave decoders are permanently connected by means of filters 150, to the master decoder.
The master decoder will therefore dialogue with all the slave decoders to create a pairing link between itself and one of the slave decoders. Only the slave decoder corresponding to the address sent will reply. But a risk of collision and multiple interference arises from this collective addressing.
Moreover, the slave furthest away from the master will be connected by means of many cascaded filters. The data sent by the master will therefore be greatly attenuated.